pvpython: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/pvpython - from package: paraview

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/pvpython - from package: paraview-python

You may install the required package with command apt-get install {package}

Error in other languages:
pvpython: bevel nie gevind nie
pvpython: comandă negăsită
pvpython: comando não encontrado
pvpython: commande introuvable
pvpython: command not found
pvpython: käsku ei ole
pvpython: không tìm thấy lệnh
pvpython: komanda nerasta
pvpython: Kommando nicht gefunden.
pvpython: kommandot finns inte
pvpython: komut yok
pvpython: nie znaleziono polecenia
pvpython: níor aimsíodh an t-ordú
pvpython: no se encontró la orden
pvpython: no s'ha trobat l'ordre
pvpython: opdracht niet gevonden
pvpython: parancs nem található
pvpython: perintah tidak ditemukan
pvpython: príkaz nenájdený
pvpython: příkaz nenalezen
pvpython: команда не найдена
pvpython: командата не е открита
pvpython: 命令找不到
pvpython: コマンドが見つかりません